Applicant's U.S. Pat. No. 8,578,695 teaches a fairly broad set of methods and top level designs for realizing engines with significantly higher efficiencies. A central result of that work is that to maximize efficiency, the power needed from the engine for the Compression cycle of an engine must be minimized. This is because the use of compression power effectively double charges the efficiency account: first by the obvious reduction of engine output by redirecting the needed compression power to the compression work of the compression cycle, but then too by that work, needing to have been produced by the engine, must thereby be produced with the penalty of the efficiency of the engine. So by example, if an engine produces a watt of power with 50% efficiency (which by the way is a very high efficiency like we are striving to attain from this invention) then that 1 watt of power was produced at the cost of 2 watts of heat input (fuel) meaning that both the compressive power is lost to the output plus an additional watt of heat input (fuel) was used above and beyond the 1 watt needed just to replace the 1 watt of compression power. This means the engine gets charged essentially twice for the compression cycle power need to run the engine, thereby significantly decreasing net efficiency.
In this specification, we will seek to disclose more detailed means for improving the efficiency of internal and external combustion engines through the use of hypocycloid mechanisms that can reduce the above referenced compression work when high power levels are not needed. For most engine applications this is the case most of the time, as vehicles tend to operate most of their time at moderate and steady loads, and the same hold true of ships and generators. However, since engines might need bursts of power periodically, the disclosed methods also can be augmented to increase the power while potentially also increase efficiency most of the time. The primary objective of this invention then is to reveal means for the practical employment of hypocycloidal mechanisms for increasing efficiency of engines.
FIGS. 1a-1e show the key descriptive figure from U.S. Pat. No. 1,579,083 issued in 1926 and is one of the older or perhaps oldest patents teaching the use of hypocycloidal gears in drive trains for internal combustion engines. However, as with all other types of prior mechanisms, it uses the easiest and lowest ratio hypocycloidal gear system with a 2:1 ratio. As can be seen in the subordinate original figures, this mechanism provides an admittedly desirable pure motion of the piston rod in-line with the cylinder axis which minimizes cylinder sidewall friction through the whole cycle. However there is no difference between the compression ratio or the expansion ratio in an engine driven with such a mechanism, and although there is a small performance and efficiency improvement from this design, it is not a large improvement.
A more refined mechanical instantiation of essentially the same basic design is shown in FIG. 2 from U.S. Pat. No. 6,510,831 B2 issued in 2003. This invention uses exactly the same hypocycloidal gear design and 2:1 ratio as shown in FIG. 1, but improves upon this with a clever integration of flat bearings to relieve the piston loads off the gears, which are less suitable for this type of reciprocating punishment. We will want to use a similar bearing design in the proposed invention for the same purpose, but will not be using the same 2:1 hypocycloidal gear ratio.
More recently, a two cylinder diametrically opposed engine with a hypocycloidal drive mechanism is described in U.S. Applicant 2010/0031916A1. This design is not unlike others (including U.S. Pat. No. 1,569,083) but differs in offering a more pragmatic mechanism that like U.S. Pat. No. 6,510,831 B2 offloads the main load from the gears onto flat bearings proven to withstand the repetitive pounding of reciprocating engines. However, once again, only a 2:1 ratio hypocycloidal gearing design is used, and all attention is given to the inline motion of the crank shaft to reduce friction between the piston and the cylinder.
U.S. Pat. No. 3,791,227 is interesting in the context of the present invention as the mechanical elements therein are similar as to what might be contemplated for instantiating the present invention in order to provide for a robust strong design. However, the entire purpose of U.S. Pat. No. 3,791,227 is for the balancing of the engine, with no thought or consideration given to the possibility of a compression versus expansion differential or other means for efficiency enhancement.
FIGS. 3a-3d from U.S. Pat. No. 6,510,831 B2 illustrate the in-line motion produced by the above inventions and all such inventions that might employ a 2:1 hypocycloidal gear ratio. Although it is enviable to provide such in-line motion, it appears this friction source was over emphasized at one time in the recent past. It absolutely is a factor, but with modern lubrication technology, it is not a key driver of engine efficiency. For example the new Honda Exlink Atkinson Linkage engine has a reduced in-line angle during the power stroke (where it really matters) but the other strokes (intake, compression and exhaust) of this engine have a larger in-line angle like most any other simple crack based engine. Therefore, although a small in-line angle may be of some importance during the power stroke when the forces are greatest, it is not a prerequisite for an efficient or usefully powerful engine at all times.